Expansion of dispersed storage network (dsn) memory

ABSTRACT

A computing device includes an interface configured to interface and communicate with a dispersed storage network (DSN), a memory that stores operational instructions, and a processing module operably coupled to the interface and memory such that the processing module, when operable within the computing device based on the operational instructions, is configured to perform various operations. A computing device identifies data slices (EDSs) of pillar width (associated with data object) to be stored within a pillar width number of a plurality of storage units (SUs). The computing device the identifies head SUs among the pillar width number of the SUs such that, based on a ring arrangement, each set of EDSs is distributedly stored among the ring arrangement of the pillar width number of the SUs starting with its respective head EDS at a respective head SU and ending with a last tail EDS at a respective last tail SU.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility patent application claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Application No. 62/248,752, entitled “MIGRATING DATA IN A DISPERSED STORAGE NETWORK,” filed Oct. 30, 2015, which is hereby incorporated herein by reference in its entirety and made part of the present U.S. Utility patent application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION

Technical Field of the Invention

This invention relates generally to computer networks and more particularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/or store data. Such computing devices range from wireless smart phones, laptops, tablets, personal computers (PC), work stations, and video game devices, to data centers that support millions of web searches, stock trades, or on-line purchases every day. In general, a computing device includes a central processing unit (CPU), a memory system, user input/output interfaces, peripheral device interfaces, and an interconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using “cloud computing” to perform one or more computing functions (e.g., a service, an application, an algorithm, an arithmetic logic function, etc.) on behalf of the computer. Further, for large services, applications, and/or functions, cloud computing may be performed by multiple cloud computing resources in a distributed manner to improve the response time for completion of the service, application, and/or function. For example, Hadoop is an open source software framework that supports distributed applications enabling application execution by thousands of computers.

In addition to cloud computing, a computer may use “cloud storage” as part of its memory system. As is known, cloud storage enables a user, via its computer, to store files, applications, etc. on an Internet storage system. The Internet storage system may include a RAID (redundant array of independent disks) system and/or a dispersed storage system that uses an error correction scheme to encode data for storage.

Within data storage systems, data storage capacity and/or memory may be added to provide for increased storage and for various other reasons. When such data storage capacity and/or memory is added, the prior art does not provide an adequate means by which the additional data storage capacity and/or memory can be easily and efficiently brought into the system and operate cooperatively with the existing/previously-provisioned data storage capacity and/or memory. There exists a need in the art for better and improved means to add data storage capacity and/or memory to such data storage systems.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed or distributed storage network (DSN) in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing core in accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an error encoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an error encoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of an encoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an error decoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of an embodiment of a Decentralized, or Distributed, Agreement Protocol (DAP) in accordance with the present invention;

FIG. 10 is a schematic block diagram of an example of creating pluralities of sets of slices in accordance with the present invention;

FIG. 11 is a schematic block diagram of an example of storage vaults in accordance with the present invention;

FIG. 12 is a schematic block diagram of an example of storing pluralities of sets of slices in accordance with the present invention;

FIG. 13 is a schematic block diagram of an example of adding a storage pool to the DSN in accordance with the present invention;

FIG. 14 is a schematic block diagram of an embodiment of a decentralized, or distributed, agreement protocol (DAP) for generating identified set of storage units in accordance with the present invention;

FIG. 15 is a schematic block diagram of an example of expansion of storage, memory, etc. of a DSN in accordance with the present invention;

FIG. 16 is a schematic block diagram of an example of a ring arrangement of storage units (SUs) within a DSN in accordance with the present invention;

FIG. 17A is a diagram illustrating an embodiment of a method for execution by one or more computing devices in accordance with the present invention; and

FIG. 17B is a diagram illustrating another embodiment of a method for execution by one or more computing devices in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, or distributed, storage network (DSN) 10 that includes a plurality of computing devices 12-16, a managing unit 18, an integrity processing unit 20, and a DSN memory 22. The components of the DSN 10 are coupled to a network 24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.), at a common site, or a combination thereof. For example, if the DSN memory 22 includes eight storage units 36, each storage unit is located at a different site. As another example, if the DSN memory 22 includes eight storage units 36, all eight storage units are located at the same site. As yet another example, if the DSN memory 22 includes eight storage units 36, a first pair of storage units are at a first common site, a second pair of storage units are at a second common site, a third pair of storage units are at a third common site, and a fourth pair of storage units are at a fourth common site. Note that a DSN memory 22 may include more or less than eight storage units 36. Further note that each storage unit 36 includes a computing core (as shown in FIG. 2, or components thereof) and a plurality of memory devices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and the integrity processing unit 20 include a computing core 26, which includes network interfaces 30-33. Computing devices 12-16 may each be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. Note that each of the managing unit 18 and the integrity processing unit 20 may be separate computing devices, may be a common computing device, and/or may be integrated into one or more of the computing devices 12-16 and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to support one or more communication links via the network 24 indirectly and/or directly. For example, interface 30 supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network 24, etc.) between computing devices 14 and 16. As another example, interface 32 supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network 24) between computing devices 12 & 16 and the DSN memory 22. As yet another example, interface 33 supports a communication link for each of the managing unit 18 and the integrity processing unit 20 to the network 24.

Computing devices 12 and 16 include a dispersed storage (DS) client module 34, which enables the computing device to dispersed storage error encode and decode data as subsequently described with reference to one or more of FIGS. 3-8. In this example embodiment, computing device 16 functions as a dispersed storage processing agent for computing device 14. In this role, computing device 16 dispersed storage error encodes and decodes data on behalf of computing device 14. With the use of dispersed storage error encoding and decoding, the DSN 10 is tolerant of a significant number of storage unit failures (the number of failures is based on parameters of the dispersed storage error encoding function) without loss of data and without the need for a redundant or backup copies of the data. Further, the DSN 10 stores data for an indefinite period of time without data loss and in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

In operation, the managing unit 18 performs DS management services. For example, the managing unit 18 establishes distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for computing devices 12-14 individually or as part of a group of user devices. As a specific example, the managing unit 18 coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within the DSN memory 22 for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The managing unit 18 facilitates storage of DS error encoding parameters for each vault by updating registry information of the DSN 10, where the registry information may be stored in the DSN memory 22, a computing device 12-16, the managing unit 18, and/or the integrity processing unit 20.

The DSN managing unit 18 creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSN module 22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particular user, a user group, a vault access, public vault access, etc. For instance, the DSN managing unit 18 tracks the number of times a user accesses a non-public vault and/or public vaults, which can be used to generate a per-access billing information. In another instance, the DSN managing unit 18 tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate a per-data-amount billing information.

As another example, the managing unit 18 performs network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, storage units, and/or computing devices with a DS client module 34) to/from the DSN 10, and/or establishing authentication credentials for the storage units 36. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the DSN 10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missing encoded data slices. At a high level, the integrity processing unit 20 performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSN memory 22. For retrieved encoded slices, they are checked for errors due to data corruption, outdated version, etc. If a slice includes an error, it is flagged as a ‘bad’ slice. For encoded data slices that were not received and/or not listed, they are flagged as missing slices. Bad and/or missing slices are subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices to produce rebuilt slices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core 26 that includes a processing module 50, a memory controller 52, main memory 54, a video graphics processing unit 55, an input/output (IO) controller 56, a peripheral component interconnect (PCI) interface 58, an IO interface module 60, at least one IO device interface module 62, a read only memory (ROM) basic input output system (BIOS) 64, and one or more memory interface modules. The one or more memory interface module(s) includes one or more of a universal serial bus (USB) interface module 66, a host bus adapter (HBA) interface module 68, a network interface module 70, a flash interface module 72, a hard drive interface module 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). The DSN interface module 76 and/or the network interface module 70 may function as one or more of the interface 30-33 of FIG. 1. Note that the IO device interface module 62 and/or the memory interface modules 66-76 may be collectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data. When a computing device 12 or 16 has data to store it disperse storage error encodes the data in accordance with a dispersed storage error encoding process based on dispersed storage error encoding parameters. The dispersed storage error encoding parameters include an encoding function (e.g., information dispersal algorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding, non-systematic encoding, on-line codes, etc.), a data segmenting protocol (e.g., data segment size, fixed, variable, etc.), and per data segment encoding values. The per data segment encoding values include a total, or pillar width, number (T) of encoded data slices per encoding of a data segment i.e., in a set of encoded data slices); a decode threshold number (D) of encoded data slices of a set of encoded data slices that are needed to recover the data segment; a read threshold number (R) of encoded data slices to indicate a number of encoded data slices per set to be read from storage for decoding of the data segment; and/or a write threshold number (W) to indicate a number of encoded data slices per set that must be accurately stored before the encoded data segment is deemed to have been properly stored. The dispersed storage error encoding parameters may further include slicing information (e.g., the number of encoded data slices that will be created for each data segment) and/or slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as the encoding function (a generic example is shown in FIG. 4 and a specific example is shown in FIG. 5); the data segmenting protocol is to divide the data object into fixed sized data segments; and the per data segment encoding values include: a pillar width of 5, a decode threshold of 3, a read threshold of 4, and a write threshold of 4. In accordance with the data segmenting protocol, the computing device 12 or 16 divides the data (e.g., a file (e.g., text, video, audio, etc.), a data object, or other data arrangement) into a plurality of fixed sized data segments (e.g., 1 through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more). The number of data segments created is dependent of the size of the data and the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a data segment using the selected encoding function (e.g., Cauchy Reed-Solomon) to produce a set of encoded data slices. FIG. 4 illustrates a generic Cauchy Reed-Solomon encoding function, which includes an encoding matrix (EM), a data matrix (DM), and a coded matrix (CM). The size of the encoding matrix (EM) is dependent on the pillar width number (T) and the decode threshold number (D) of selected per data segment encoding values. To produce the data matrix (DM), the data segment is divided into a plurality of data blocks and the data blocks are arranged into D number of rows with Z data blocks per row. Note that Z is a function of the number of data blocks created from the data segment and the decode threshold number (D). The coded matrix is produced by matrix multiplying the data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encoding with a pillar number (T) of five and decode threshold number of three. In this example, a first data segment is divided into twelve data blocks (D1-D12). The coded matrix includes five rows of coded data blocks, where the first row of X11-X14 corresponds to a first encoded data slice (EDS 1_1), the second row of X21-X24 corresponds to a second encoded data slice (EDS 2_1), the third row of X31-X34 corresponds to a third encoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to a fourth encoded data slice (EDS 4_1), and the fifth row of X51-X54 corresponds to a fifth encoded data slice (EDS 5_1). Note that the second number of the EDS designation corresponds to the data segment number.

Returning to the discussion of FIG. 3, the computing device also creates a slice name (SN) for each encoded data slice (EDS) in the set of encoded data slices. A typical format for a slice name 60 is shown in FIG. 6. As shown, the slice name (SN) 60 includes a pillar number of the encoded data slice (e.g., one of 1-T), a data segment number (e.g., one of 1-Y), a vault identifier (ID), a data object identifier (ID), and may further include revision level information of the encoded data slices. The slice name functions as, at least part of, a DSN address for the encoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces a plurality of sets of encoded data slices, which are provided with their respective slice names to the storage units for storage. As shown, the first set of encoded data slices includes EDS 1_1 through EDS 5_1 and the first set of slice names includes SN 1_1 through SN 5_1 and the last set of encoded data slices includes EDS 1_Y through EDS 5_Y and the last set of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of a data object that was dispersed storage error encoded and stored in the example of FIG. 4. In this example, the computing device 12 or 16 retrieves from the storage units at least the decode threshold number of encoded data slices per data segment. As a specific example, the computing device retrieves a read threshold number of encoded data slices.

To recover a data segment from a decode threshold number of encoded data slices, the computing device uses a decoding function as shown in FIG. 8. As shown, the decoding function is essentially an inverse of the encoding function of FIG. 4. The coded matrix includes a decode threshold number of rows (e.g., three in this example) and the decoding matrix in an inversion of the encoding matrix that includes the corresponding rows of the coded matrix. For example, if the coded matrix includes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2, and 4, and then inverted to produce the decoding matrix.

FIG. 9 is a schematic block diagram 900 of an embodiment of a Decentralized, or Distributed, Agreement Protocol (DAP) 80 that may be implemented by a computing device, a storage unit, and/or any other device or unit of the DSN to determine where to store encoded data slices or where to find stored encoded data slices. The DAP 80 includes a plurality of functional rating modules 81. Each of the functional rating modules 81 includes a deterministic function 83, a normalizing function 85, and a scoring function 87.

Each functional rating module 81 receives, as inputs, a slice identifier 82 and storage pool (SP) coefficients (e.g., a first functional rating module 81-1 receives SP 1 coefficients “a” and b). Based on the inputs, where the SP coefficients are different for each functional rating module 81, each functional rating module 81 generates a unique score 93 (e.g., an alpha-numerical value, a numerical value, etc.). The ranking function 84 receives the unique scores 93 and orders them based on an ordering function (e.g., highest to lowest, lowest to highest, alphabetical, etc.) and then selects one as a selected storage pool 86. Note that a storage pool includes one or more sets of storage units 86. Further note that the slice identifier 82 corresponds to a slice name or common attributes of set of slices names. For example, for a set of encoded data slices, the slice identifier 120 specifies a data segment number, a vault ID, and a data object ID, but leaves open ended, the pillar number. As another example, the slice identifier 82 specifies a range of slice names (e.g., 0000 0000 to FFFF FFFF).

As a specific example, the first functional module 81-1 receives the slice identifier 82 and SP coefficients for storage pool 1 of the DSN. The SP coefficients includes a first coefficient (e.g., “a”) and a second coefficient (e.g., “b”). For example, the first coefficient is a unique identifier for the corresponding storage pool (e.g., SP #1's ID for SP 1 coefficient “a”) and the second coefficient is a weighting factor for the storage pool. The weighting factors are derived to ensure, over time, data is stored in the storage pools in a fair and distributed manner based on the capabilities of the storage units within the storage pools.

For example, the weighting factor includes an arbitrary bias which adjusts a proportion of selections to an associated location such that a probability that a source name will be mapped to that location is equal to the location weight divided by a sum of all location weights for all locations of comparison (e.g., locations correspond to storage units). As a specific example, each storage pool is associated with a location weight factor based on storage capacity such that, storage pools with more storage capacity have a higher location weighting factor than storage pools with less storage capacity.

The deterministic function 83, which may be a hashing function, a hash-based message authentication code function, a mask generating function, a cyclic redundancy code function, hashing module of a number of locations, consistent hashing, rendezvous hashing, and/or a sponge function, performs a deterministic function on a combination and/or concatenation (e.g., add, append, interleave) of the slice identifier 82 and the first SP coefficient (e.g., SU 1 coefficient “a”) to produce an interim result 89.

The normalizing function 85 normalizes the interim result 89 to produce a normalized interim result 91. For instance, the normalizing function 85 divides the interim result 89 by a number of possible output permutations of the deterministic function 83 to produce the normalized interim result. For example, if the interim result is 4,325 (decimal) and the number of possible output permutations is 10,000, then the normalized result is 0.4325.

The scoring function 87 performs a mathematical function on the normalized result 91 to produce the score 93. The mathematical function may be division, multiplication, addition, subtraction, a combination thereof, and/or any mathematical operation. For example, the scoring function divides the second SP coefficient (e.g., SP 1 coefficient “b”) by the negative log of the normalized result (e.g., e^(y)=x and/or ln(x)=y). For example, if the second SP coefficient is 17.5 and the negative log of the normalized result is 1.5411 (e.g., e^((0.4235))), the score is 11.3555.

The ranking function 84 receives the scores 93 from each of the function rating modules 81 and orders them to produce a ranking of the storage pools. For example, if the ordering is highest to lowest and there are five storage units in the DSN, the ranking function evaluates the scores for five storage units to place them in a ranked order. From the ranking, the ranking module 84 selects one the storage pools 86, which is the target for a set of encoded data slices.

The DAP 80 may further be used to identify a set of storage units, an individual storage unit, and/or a memory device within the storage unit. To achieve different output results, the coefficients are changed according to the desired location information. The DAP 80 may also output the ranked ordering of the scores.

FIG. 10 is a schematic block diagram 1000 of an example of creating pluralities of sets of slices. Each plurality of sets of encoded data slices (EDSs) corresponds to the encoding of a data object, a portion of a data object, or multiple data object, where a data object is one or more of a file, text, data, digital information, etc. For example, the highlighted plurality of encoded data slices corresponds to a data object having a data identifier of “a2”.

Each encoded data slices of each set of encoded data slices is uniquely identified by its slice name, which is also used as at least part of the DSN address for storing the encoded data slice. As shown, a set of EDSs includes EDS 1_1_1_a1 through EDS 5_1_1_a1. The EDS number includes pillar number, data segment number, vault ID, and data object ID. Thus, for EDS 1_1_1_a1, it is the first EDS of a first data segment of data object “a1” and is to be stored, or is stored, in vault 1. Note that vaults are a logical memory container supported by the storage units of the DSN. A vault may be allocated to one or more user computing devices.

As is further shown, another plurality of sets of encoded data slices are stored in vault 2 for data object “b1”. There are Y sets of EDSs, where Y corresponds to the number of data segments created by segmenting the data object. The last set of EDSs of data object “b1” includes EDS 1_Y_2_b_1 through EDS 5_Y_2_b1. Thus, for EDS 1_Y_2_b1, it is the first EDS of the last data segment “Y” of data object “b1” and is to be stored, or is stored, in vault 2.

FIG. 11 is a schematic block diagram 1100 of an example of storage vaults spanning multiple storage pools. In this example, the DSN memory 22 includes a plurality of storage units 36 arranged into a plurality of storage pools (e.g., 1-n). In this example, each storage pool includes seven storage units for ease of illustration. A storage pool, however, can have many more storage units than seven and, from storage pool to storage pool, may have different numbers of storage units.

The storage pools 1-n support two vaults (vault 1 and vault 2) using only five of seven of the storage units. The number of storage units within a vault correspond to the pillar width number, which is five in this example. Note that a storage pool may have rows of storage units, where SU #1 represents a plurality of storage units, each corresponding to a first pillar number; SU #2 represents a second plurality of storage units, each corresponding to a second pillar number; and so on. Note that other vaults may use more or less than a width of five storage units.

FIG. 12 is a schematic block diagram 1200 of an example of storing pluralities of sets of slices in accordance with the Decentralized, or Distributed, Agreement Protocol (DAP) 80 of FIG. 9. The DAP 80 uses slice identifiers (e.g., the slice name or common elements thereof (e.g., the pillar number, the data segment number, the vault ID, and/or the data object ID)) to identify, for one or more sets of encoded data slices, a set, or pool, of storage units. With respect to the three pluralities of sets of encoded data slices (EDSs) of FIG. 11, the DAP 80 approximately equally distributes the sets of encoded data slices throughout the DSN memory (e.g., among the various storage units).

The first column corresponds to storage units having a designation of SU #1 in their respective storage pool or set of storage units and stores encoded data slices having a pillar number of 1. The second column corresponds to storage units having a designation of SU #2 in their respective storage pool or set of storage units and stores encoded data slices having a pillar number of 2, and so on. Each column of EDSs is divided into one or more groups of EDSs. The delineation of a group of EDSs may correspond to a storage unit, to one or more memory devices within a storage unit, or multiple storage units. Note that the grouping of EDSs allows for bulk addressing, which reduces network traffic.

A range of encoded data slices (EDSs) spans a portion of a group, spans a group, or spans multiple groups. The range may be numerical range of slice names regarding the EDSs, one or more source names (e.g., common aspect shared by multiple slice names), a sequence of slice names, or other slice selection criteria.

FIG. 13 is a schematic block diagram 1300 of an example of adding a storage pool to the DSN. In this example storage pool n+1 is added and is supporting vaults 1 and 2. As result, the Decentralized, or Distributed, Agreement Protocol (DAP) 80 of FIG. 9 is changed to include another functional rating module 81 for the new storage pool and the second coefficients (e.g., “b”, which correspond to the weight factor) are adjusted for some, if not all, of the other functional rating modules 81. As a result of changing the DAP 80, storage responsibility for encoded data slices is going to change, causing them to be transferred between the storage units. When there are significant numbers of encoded data slices to be transferred and there are hundreds to tens of thousands of resources in the DSN (e.g., computing devices, storage units, managing units, integrity units performing rebuilding, etc.), the updating of the DSN is complex and time consuming.

While the DSN is being updated based on the new DAP, data access requests, listing requests, and other types of requests regarding the encoded data slices are still going to be received and need to be processed in a timely manner. Such requests will be based on the old DAP. As such, a request for an encoded data slice (EDS), or information about the EDS, will go to the storage unit identified using the DAP 80 prior to updating it. If the storage unit has already transferred the EDS to the storage unit identified using the new DAP 80, then the storage unit functions as proxy for the new storage unit and the requesting device.

FIG. 14 is a schematic block diagram 1400 of an embodiment of a decentralized, or distributed, agreement protocol (DAP) for generating identified set of storage units in accordance with the present invention. The DAP 80 is similar to the DAP of FIG. 9, but uses a slice identifier 120 instead of a source name 82, uses coefficients for a set of storage units instead of for individual storage units, and the ranking function 84 outputs an identified set of storage units 122 instead of a storage unit ranking 86. The slice identifier 120 corresponds to a slice name or common attributes of set of slices names. For example, for a set of encoded data slices, the slice identifier 120 specifies a data segment number, a vault ID, and a data object ID, but leaves open ended, the pillar number.

In an example of the operation, each of the functional rating modules 81 generates a score 93 for each set of the storage units based on the slice identifier 120. The ranking function 84 orders the scores 93 to produce a ranking. But, instead of outputting the ranking, the ranking function 84 outputs one of the scores, which corresponds to the identified set of storage units.

As can be seen, such a DAP may be implemented and executed for many different applications including for the determination of where to store encoded data slices or where to find stored encoded data slices such as with respect to FIG. 9 as well as the identification of a set of storage units (SUs) such as with respect to FIG. 14. Based on differently provided input to the DAP, differently provided information may be output. Generally speaking, the more detailed information is that is provided to the DAP, then the more detailed information will be output when from the DAP when executed.

FIG. 15 is a schematic block diagram of an example 1500 of expansion of storage, memory, etc. of a DSN in accordance with the present invention. Within a DSN, memory, SU(s), etc. may be added to existing SUs (e.g., SUs #1-5 36) for various reasons. The SU and EDSs depicted within this diagram may be understood prior diagrams including FIG. 3, FIG. 7, among others. In some examples, when a SU is added (e.g., based on SU #6 36), the dispersed error encoding (DSE) parameters may be modified such that the pillar width of the DSE parameters is expanded and one or more additional pillars is generated based on encoding of the data segments. In other examples, when a SU Is added (e.g., based on SU #7 36 or different respective SUs, #7a-7b 36, for each respective pillars), the DSE parameters may be modified such that one or more additional segments is generated when a data object is segmented into data segments. The additional pillar of encoded data slices (EDSs) generated from the DSE of the data segments and/or an additional set of EDSs may be included within the additional one or more SUs that get provisioned to the DSN. This disclosure presents various means by which efficient expansion of DSN memory may be expanded. In some examples, expansion of DSN memory may be expanded by one SU at a time.

FIG. 16 is a schematic block diagram of an example 1600 of a ring arrangement of storage units (SUs) within a DSN in accordance with the present invention. While the particular configuration and locations of SUs #1-7 36 may be arranged in any particular manner, a ring arrangement (e.g., which may be conceptual) may be used to manage and operate the SUs of the DSN. For example, consider that SUs #1-7 36 are arranged based on a ring arrangement such that sets of EDSs are distributedly stored among the ring arranged SUs #1-7 36 such that the first EDS of each set of EDSs is stored in a head SU for that particular EDS set based on a corresponding data segment that has undergone DSE and is followed by tail SUs in which the subsequent EDSs of that particular EDS set are distributedly stored and terminated with a last tail SU that stored a last tail EDS of that particular EDS set.

For example, EDS 1_1 (head EDS of EDS set #1 based on data segment #1 that has undergone DSE) is stored in its head SU, SU #2 36, EDS 2_1 (2^(nd) EDS of EDS set #1 based on data segment #1 that has undergone DSE) is stored in SU #3 36, EDS 3_1 (3^(rd) EDS of EDS set #1 based on data segment #1 that has undergone DSE) is stored in SU #3 36, and so on until EDS 5_1 (5^(th)/last tail EDS of EDS set #1 based on data segment #1 that has undergone DSE) is stored in its last tail SU #6 36. Similarly, other sets of EDS are distributedly stored within the SUs #1-7 36 starting at a respective head SU, followed by intervening EDSs of that EDS set being distributedly stored in subsequent SUs and so on until the last tail EDS of that EDS set is stored in its last tail SU. Note that the respective head SUs of the respective EDS sets may be staggered based on the ring arrangement of SUs within the DSN. The staggering of the head SUs may be one single SU, two SUs, etc. (e.g., generally any positive integer number N, where N=1, 2, etc.) and the staggering may be same or different throughout the SUs #1-7 36. Note also that the distributedly storing of the EDS sets within the SUs #1-7 36 based on the ring arrangement may be made in a clockwise or counter-clockwise manner without departing from the scope and spirit of the invention.

Then, one or more SUs (e.g., SU #8 36) is added to the SUs #1-7 36. In some examples, certain EDSs are reallocated from the SUs #1-7 36 to the SU #8 36 to ensure a more evenly distributed allocation of the EDSs among all of the SUs #1-8 36. This efficient expansion of memory within a DSN allows for even addition of as few as one SU at a time to the pool of SUs.

In an example of operation and implementation, a computing device includes an interface configured to interface and communicate with a dispersed storage network (DSN), a memory that stores operational instructions, and a processing module operably coupled to the interface and memory such that the processing module, when operable within the computing device based on the operational instructions, is configured to perform various operations.

In one example, the computing device identifies encoded data slices (EDSs) of pillar width and associated with a data object to be stored within a plurality of storage units (SUs). Note that the data object is segmented into a plurality of data segments, and a data segment of the plurality of data segments is dispersed error encoded in accordance with dispersed error encoding parameters to produce a set of EDSs that includes a head EDS followed by tail EDSs. Note also that the number of SUs may be same or different (e.g., more) than the pillar width. For example, the SUs may include 5 SUs when the pillar width is 5. Alternatively, SUs may include 7 SUs when the pillar width is 5. The EDS sets are then distributedly stored within the SUs #1-7 36 starting at a respective head SU for each respective EDS set. Note that when the EDS sets include fewer EDSs than the plurality of SUs includes SUs, each respective EDS set will not necessarily wrap around and include EDSs within each of the respective SUs (e.g., if pillar width is 5 and SUs include more than 5 SUs, then at least one of the SUs will not include a respective EDS from that given EDS set).

The computing device the identifies a plurality of head SUs among the plurality of SUs such that, based on a ring arrangement of the plurality of SUs, each set of EDSs being distributedly stored among the ring arrangement of the plurality of SUs starting with its respective head EDS at a respective head SU and ending with a last tail EDS at a respective last tail SU, wherein the plurality of head SUs are staggered among the ring arrangement of the plurality of SUs.

In some examples, the computing device also identifies the plurality of head SUs based on a first system configuration of a Decentralized, or Distributed, Agreement Protocol (DAP) for the plurality of SUs. Then, the computing device generates, based on addition of a SU to the plurality of SUs to generate another plurality of SUs, a second system configuration of the DAP for the other plurality of SUs. the computing device then identifies, based on difference between the first system configuration of the DAP for the plurality of SUs to the second system configuration of the DAP for the another plurality of SUs, a number of head EDSs and a number of tail EDSs to transfer from head SUs and tail SUs to the SU added to the plurality of SUs to generate the another plurality of SUs, and the computing device then transfers the number of head EDSs and the number of tail EDSs to the SU added to the plurality of SUs to generate the another plurality of SUs. Note that the different system configurations of the DAP may be based on different numbers of SUs (e.g., first system configuration of the DAP based on 7 SUs

In certain examples, note that a first head EDS of a first set of EDSs is stored in a first head SU of the plurality of SUs followed by first tail EDSs of the first set of EDSs and ending with a last tail EDS of the first tail EDSs stored in a first last tail SU of the plurality of SUs, and a second head EDS of a second set of EDSs is stored in a second head SU of the plurality of SUs followed by second tail EDSs of the second set of EDSs and ending with a last tail EDS of the second tail EDSs stored in a second last tail SU of the plurality of SUs, wherein the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.

In certain other examples, note that a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as same amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.

In addition, in even other examples, note that a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as different amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.

Note that the computing device may be located at a first premises that is remotely located from at least one SU of the primary SUs or plurality of secondary SUs the within the DSN. Also, note that the computing device may be of any of a variety of types of devices as described herein and/or their equivalents including a SU of the primary SUs or the secondary SUs within the DSN, a wireless smart phone, a laptop, a tablet, a personal computers (PC), a work station, and/or a video game device. Note also that the DSN may be implemented to include or be based on any of a number of different types of communication systems including a wireless communication system, a wire lined communication systems, a non-public intranet system, a public internet system, a local area network (LAN), and/or a wide area network (WAN).

FIG. 17A is a diagram illustrating an embodiment of a method 1701 for execution by one or more computing devices in accordance with the present invention. The method 1701 begins in step 1710 by identifying a plurality of encoded data slices (EDSs) of pillar width and associated with a data object to be stored within a plurality of storage units (SUs) of a dispersed storage network (DSN). Note that the data object is segmented into a plurality of data segments, and a data segment of the plurality of data segments is dispersed error encoded in accordance with dispersed error encoding parameters to produce a set of EDSs that includes a head EDS followed by tail EDSs.

The method 1702 continues in step 1720 by identifying a plurality of head SUs among the plurality of SUs such that, based on a ring arrangement of the plurality of SUs, each set of EDSs being distributedly stored among the ring arrangement of the plurality of SUs starting with its respective head EDS at a respective head SU and ending with a last tail EDS at a respective last tail SU, wherein the plurality of head SUs are staggered among the ring arrangement of the plurality of SUs. Note that the method 1701 also operates by distributedly storing sets of EDSs among the ring arrangement of SUs in step 1722. This may be performed such that each set of EDSs begins at a respective head SU and continues with tail SUs and then ends with a last tail SU.

In some examples, the method 1702 continues in step 1724 by distributedly storing a first head EDS of a first set of EDSs beginning in a first head SU of the plurality of SUs followed by first tail EDSs of the first set of EDSs and ending with a last tail EDS of the first tail EDSs stored in a first last tail SU of the plurality of SUs. The method 1702 also continues in step 1726 by distributedly storing a second head EDS of a second set of EDSs beginning in a second head SU of the plurality of SUs followed by second tail EDSs of the second set of EDSs and ending with a last tail EDS of the second tail EDSs stored in a second last tail SU of the plurality of SUs.

Note that the second head SU may be staggered from the first head SU among the ring arrangement of the plurality of SUs if desired in some examples. Note also that any staggering between head SUs of the respective sets of EDSs may be same or different throughout the SUs (e.g., same/uniform staggering among the head SUs throughout the SUs, or first staggering such as 1 between first and second head SU and second staggering such as 2 between second and third head SU, and/or any desired combination thereof).

FIG. 17B is a diagram illustrating another embodiment of a method 1702 for execution by one or more computing devices in accordance with the present invention. The method 1702 begins in step 1711 by identifying a plurality of head SUs based on a first system configuration of a Decentralized, or Distributed, Agreement Protocol (DAP) for the plurality of SUs. Then, the method 1702 operates by operating the SUs of the DSN based on the first system configuration of the DAP in step 1721. The method 1702 operates to determine whether an SU has been added to the DSN in step 1731. When no SU has been added, then the method 1702 continues by operating the SUs of the DSN based on the first system configuration of the DAP in step 1721. Alternatively when a SU has been added the method 1702 operates by generating, based on addition of a SU to the plurality of SUs that generates another plurality of SUs, a second system configuration of the DAP for the another plurality of SUs in step 1741.

The method 1702 then operates by identifying, based on difference between the first system configuration of the DAP for the plurality of SUs to the second system configuration of the DAP for the another plurality of SUs, a number of head EDSs and a number of tail EDSs to transfer from head SUs and tail SUs to the SU added to the plurality of SUs to generate the another plurality of SUs. The method 1702 then operates in step 1761 by transferring the number of head EDSs and the number of tail EDSs to the SU added to the plurality of SUs to generate the another plurality of SUs.

This disclosure presents, among other things, novel means for efficient allocation of EDSs among SUs including accommodating the situation when one or more SUs are added to the pool of SUs. This disclosure presents, among other things, novel means for substantially evenly distribution of the EDSs among the SUs to be used including moving EDSs from certain of the SUs to the newly added one or more SUs to provide for substantially evenly distribution of the EDSs among the SUs.

In some examples, when the namespace is used to place EDSs, this has optimal reliability characteristics, as there is a minimum number of “logical stripes”—unique combinations for selecting a set of width SUs on which to store an EDS. However, it has worst-case cost for rebalancing data utilization upon the insertion of a single SU. This is because that one SU addition changes the namespace boundaries for all existing SUs. For example, if there were N SUs, then each SU owns a (1/N) fraction of the namespace. If one SU is added in this model, all SUs must transition to owning a (1/(N+1)) fraction of the namespace. This can lead to up to half of the data in the system from having to move. On the other hand, an approach for selecting which information dispersal algorithm (IDA) Width (e.g., based on dispersed error encoding (DSE) parameters) number of SUs out of the N existing SUs, e.g. based on a Decentralized Agreement Protocol, has optimal efficiency characteristics (only one SU's worth of data must move) but worst case reliability impact: there are now (N choose IDA Width) combinations for how SUs can be selected for storing EDSs, which makes data loss events many times more likely. A trade-off exists in which has close to optimal data movement with only a linear decrease in reliability. In this approach, the SUs are arranged in a conceptual ring (e.g., ring arrangement). A deterministic function, e.g. a DAP, is then used to select a “head SU” for any source stored in the system. The head SU receives the first EDS of the source, and the (Width−1) following SUs are the “tail SUs” which each receive one EDS of the source. Upon the addition of any SU, some fraction of sources (with the fraction equal to (1/N)) transition their head to this newly added SU. The newly added SU also displaces some tail SUs as well, and receives some EDSs from those tail SUs. When imposter EDSs exist, it does not require that an IDA Width number of tail EDSs be moved to accommodate this insertion. The total data movement is equal to up to twice a SU's worth of data, and the number of combinations (or logical stripes) for storing EDSs in the system is equal to N, which is higher than (N/IDA Width) for the namespace approach, but only worse by a factor of IDA Width.

It is noted that terminologies as may be used herein such as bit stream, stream, signal sequence, etc. (or their equivalents) have been used interchangeably to describe digital information whose content corresponds to any of a number of desired types (e.g., data, video, speech, audio, etc. any of which may generally be referred to as ‘data’).

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “configured to”, “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for an example of indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “configured to”, “operable to”, “coupled to”, or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1. As may be used herein, the term “compares unfavorably”, indicates that a comparison between two or more items, signals, etc., fails to provide the desired relationship.

As may also be used herein, the terms “processing module”, “processing circuit”, “processor”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the figures. Such a memory device or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claims. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claims. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.

In addition, a flow diagram may include a “start” and/or “continue” indication. The “start” and “continue” indications reflect that the steps presented can optionally be incorporated in or otherwise used in conjunction with other routines. In this context, “start” indicates the beginning of the first step presented and may be preceded by other activities not specifically shown. Further, the “continue” indication reflects that the steps presented may be performed multiple times and/or may be succeeded by other activities not specifically shown. Further, while a flow diagram indicates a particular ordering of steps, other orderings are likewise possible provided that the principles of causality are maintained.

The one or more embodiments are used herein to illustrate one or more aspects, one or more features, one or more concepts, and/or one or more examples. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of the embodiments. A module implements one or more functions via a device such as a processor or other processing device or other hardware that may include or operate in association with a memory that stores operational instructions. A module may operate independently and/or in conjunction with software and/or firmware. As also used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes one or more memory elements. A memory element may be a separate memory device, multiple memory devices, or a set of memory locations within a memory device. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. The memory device may be in a form a solid state memory, a hard drive memory, cloud memory, thumb drive, server memory, computing device memory, and/or other physical medium for storing digital information.

While particular combinations of various functions and features of the one or more embodiments have been expressly described herein, other combinations of these features and functions are likewise possible. The present disclosure is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A computing device comprising: an interface configured to interface and communicate with a dispersed storage network (DSN); memory that stores operational instructions; and a processing module operably coupled to the interface and to the memory, wherein the processing module, when operable within the computing device based on the operational instructions, is configured to: identify a plurality of encoded data slices (EDSs) of pillar width and associated with a data object to be stored within a plurality of storage units (SUs), wherein the data object is segmented into a plurality of data segments, and wherein a data segment of the plurality of data segments is dispersed error encoded in accordance with dispersed error encoding parameters to produce a set of EDSs that includes a head EDS followed by tail EDSs; and identify a plurality of head SUs among the plurality of SUs such that, based on a ring arrangement of the plurality of SUs, each set of EDSs being distributedly stored among the ring arrangement of the plurality of SUs starting with its respective head EDS at a respective head SU and ending with a last tail EDS at a respective last tail SU, wherein the plurality of head SUs are staggered among the ring arrangement of the plurality of SUs.
 2. The computing device of claim 1, wherein the processing module, when operable within the computing device based on the operational instructions, is further configured to: identify the plurality of head SUs based on a first system configuration of a Decentralized, or Distributed, Agreement Protocol (DAP) for the plurality of SUs; generate, based on addition of a SU to the plurality of SUs to generate another plurality of SUs, a second system configuration of the DAP for the another plurality of SUs; identify, based on difference between the first system configuration of the DAP for the plurality of SUs to the second system configuration of the DAP for the another plurality of SUs, a number of head EDSs and a number of tail EDSs to transfer from head SUs and tail SUs to the SU added to the plurality of SUs to generate the another plurality of SUs; and transfer the number of head EDSs and the number of tail EDSs to the SU added to the plurality of SUs to generate the another plurality of SUs.
 3. The computing device of claim 1, wherein: a first head EDS of a first set of EDSs is stored in a first head SU of the plurality of SUs followed by first tail EDSs of the first set of EDSs and ending with a last tail EDS of the first tail EDSs stored in a first last tail SU of the plurality of SUs; and a second head EDS of a second set of EDSs is stored in a second head SU of the plurality of SUs followed by second tail EDSs of the second set of EDSs and ending with a last tail EDS of the second tail EDSs stored in a second last tail SU of the plurality of SUs, wherein the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 4. The computing device of claim 3, wherein: a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as same amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 5. The computing device of claim 3, wherein: a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as different amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 6. The computing device of claim 1, wherein the computing device is located at a first premises that is remotely located from at least one SU of the plurality of SUs within the DSN.
 7. The computing device of claim 1 further comprising: a SU of the plurality of SUs within the DSN, a wireless smart phone, a laptop, a tablet, a personal computers (PC), a work station, or a video game device.
 8. The computing device of claim 1, wherein the DSN includes at least one of a wireless communication system, a wire lined communication systems, a non-public intranet system, a public internet system, a local area network (LAN), or a wide area network (WAN).
 9. A computing device comprising: an interface configured to interface and communicate with a dispersed storage network (DSN); memory that stores operational instructions; and a processing module operably coupled to the interface and to the memory, wherein the processing module, when operable within the computing device based on the operational instructions, is configured to: identify a plurality of encoded data slices (EDSs) of pillar width and associated with a data object to be stored within a plurality of storage units (SUs), wherein the data object is segmented into a plurality of data segments, and wherein a data segment of the plurality of data segments is dispersed error encoded in accordance with dispersed error encoding parameters to produce a set of EDSs that includes a head EDS and a tail EDS; identify, based on a first system configuration of a Decentralized, or Distributed, Agreement Protocol (DAP) for the plurality of SUs, a plurality of head SUs among the plurality of SUs such that, based on a ring arrangement of the plurality of SUs, each set of EDSs is distributedly stored among the ring arrangement of the plurality of SUs starting with its respective head EDS at a respective head SU and ending with its respective tail EDS at a respective tail SU, wherein the plurality of head SUs are staggered among the ring arrangement of the plurality of SUs; generate, based on addition of a SU to the plurality of SUs to generate another plurality of SUs, a second system configuration of the DAP for the another plurality of SUs; identify, based on difference between the first system configuration of the DAP for the plurality of SUs to the second system configuration of the DAP for the another plurality of SUs, a number of head EDSs and a number of tail EDSs to transfer from head SUs and tail SUs to the SU added to the plurality of SUs to generate the another plurality of SUs; and transfer the number of head EDSs and the number of tail EDSs to the SU added to the plurality of SUs to generate the another plurality of SUs to balance substantially storage of the plurality of EDSs among the another plurality of SUs.
 10. The computing device of claim 9, wherein the processing module, when operable within the computing device based on the operational instructions, is further configured to: a first head EDS of a first set of EDSs is stored in a first head SU of the plurality of SUs followed by first tail EDSs of the first set of EDSs and ending with a last tail EDS of the first tail EDSs stored in a first last tail SU of the plurality of SUs; and a second head EDS of a second set of EDSs is stored in a second head SU of the plurality of SUs followed by second tail EDSs of the second set of EDSs and ending with a last tail EDS of the second tail EDSs stored in a second last tail SU of the plurality of SUs, wherein the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 11. The computing device of claim 10, wherein: a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as same amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 12. The computing device of claim 9 further comprising: a SU of the plurality of SUs within the DSN, a wireless smart phone, a laptop, a tablet, a personal computers (PC), a work station, or a video game device.
 13. The computing device of claim 9, wherein the DSN includes at least one of a wireless communication system, a wire lined communication systems, a non-public intranet system, a public internet system, a local area network (LAN), or a wide area network (WAN).
 14. A method for execution by a computing device, the method comprising: identifying a plurality of encoded data slices (EDSs) of pillar width and associated with a data object to be stored within a plurality of storage units (SUs) of a dispersed storage network (DSN), wherein the data object is segmented into a plurality of data segments, and wherein a data segment of the plurality of data segments is dispersed error encoded in accordance with dispersed error encoding parameters to produce a set of EDSs that includes a head EDS followed by tail EDSs; and identifying a plurality of head SUs among the plurality of SUs such that, based on a ring arrangement of the plurality of SUs, each set of EDSs being distributedly stored among the ring arrangement of the plurality of SUs starting with its respective head EDS at a respective head SU and ending with a last tail EDS at a respective last tail SU, wherein the plurality of head SUs are staggered among the ring arrangement of the plurality of SUs.
 15. The method of claim 14 further comprising: identifying the plurality of head SUs based on a first system configuration of a Decentralized, or Distributed, Agreement Protocol (DAP) for the plurality of SUs; generating, based on addition of a SU to the plurality of SUs that generates another plurality of SUs, a second system configuration of the DAP for the another plurality of SUs; identifying, based on difference between the first system configuration of the DAP for the plurality of SUs to the second system configuration of the DAP for the another plurality of SUs, a number of head EDSs and a number of tail EDSs to transfer from head SUs and tail SUs to the SU added to the plurality of SUs to generate the another plurality of SUs; and transferring the number of head EDSs and the number of tail EDSs to the SU added to the plurality of SUs to generate the another plurality of SUs.
 16. The method of claim 14, wherein: a first head EDS of a first set of EDSs is stored in a first head SU of the plurality of SUs followed by first tail EDSs of the first set of EDSs and ending with a last tail EDS of the first tail EDSs stored in a first last tail SU of the plurality of SUs; and a second head EDS of a second set of EDSs is stored in a second head SU of the plurality of SUs followed by second tail EDSs of the second set of EDSs and ending with a last tail EDS of the second tail EDSs stored in a second last tail SU of the plurality of SUs, wherein the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 17. The method of claim 16, wherein: a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as same amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 18. The method of claim 16, wherein: a third head EDS of a third set of EDSs is stored in a third head SU of the plurality of SUs followed by third tail EDSs of the third set of EDSs and ending with a last tail EDS of the third tail EDSs stored in a third last tail SU of the plurality of SUs, wherein the third head SU is staggered from the second head SU among the ring arrangement of the plurality of SUs by as different amount that the second head SU is staggered from the first head SU among the ring arrangement of the plurality of SUs.
 19. The method of claim 14, wherein the computing device is a SU of the plurality of SUs within the DSN, a wireless smart phone, a laptop, a tablet, a personal computers (PC), a work station, or a video game device.
 20. The method of claim 14, wherein the DSN includes at least one of a wireless communication system, a wire lined communication systems, a non-public intranet system, a public internet system, a local area network (LAN), or a wide area network (WAN). 